A method of manufacturing a transformer is disclosed. A first bobbin piece, having a first channel and a primary winding section is provided. A second bobbin comprising first and second secondary side plates, plural partition plates, a wall portion, a secondary base having a first pin arranged on a bottom surface of the secondary base, plural secondary winding sections, and a second channel is provided. A second pin is inserted into the second bobbin piece to form a wire-arranging part protruded from the second secondary side plate and an insertion part protruded from the bottom surface of the secondary base. A primary winding coil is wound on the primary winding section, and the first and second terminals of a secondary winding coil are respectively fixed on the first pin and the wire-arranging part. A magnetic core assembly is partially disposed within the first channel and the second channel.

Claim:

What is claimed is:

1. A method of manufacturing a transformer, comprising steps of: providing a first bobbin piece having a first channel therein and a primary winding section; providing asecond bobbin piece comprising a first secondary side plate, a second secondary side plate opposed to said first secondary side plate, a plurality of partition plates between said first secondary side plate and said second secondary side plate, a wallportion between every two adjacent partition plates, and a secondary base extended from an edge of said first secondary side plate and having a first pin arranged on a bottom surface of said secondary base, wherein a plurality of secondary windingsections are defined by every two adjacent partition plates, and a second channel is defined within said wall portion; inserting a second pin into said second bobbin piece to penetrate through said wall portion and said second secondary side plate andform a wire-arranging part protruded from said second secondary side plate and an insertion part protruded from said bottom surface of said secondary base; winding a primary winding coil on said primary winding section; fixing a first terminal of asecondary winding coil on said first pin, winding said secondary winding coil on said secondary winding sections and fixing a second terminal of said secondary winding coil on said wire-arranging part of said second pin; and partially disposing amagnetic core assembly within said first channel of said first bobbin piece and said second channel of said second bobbin piece.

2. The method of manufacturing the transformer according to claim 1 wherein said first secondary side plate, said second secondary side plate and said partition plates are parallel with each other.

3. The method of manufacturing the transformer according to claim 1 wherein each of said partition plates has a notch such that said secondary winding coil is successively wound on said secondary winding sections through said notch.

4. The method of manufacturing the transformer according to claim 1 wherein said second pin further includes an intermediate part defined between said wire-arranging part and said insertion part and buried in said wall portion of said secondbobbin piece.

5. The method of manufacturing the transformer according to claim 1 wherein said second pin has a gradually increasing width, and said wire-arranging part has a smaller width.

6. The method of manufacturing the transformer according to claim 1 wherein said second pin has an even width.

7. The method of manufacturing the transformer according to claim 1 further comprising a step of bending a rear end of said second pin to form said insertion part.

8. The method of manufacturing the transformer according to claim 1 wherein said first bobbin piece further includes a covering element for partially receiving said second bobbin piece therein.

9. The method of manufacturing the transformer according to claim 8 further comprising a step of disposing parts of said second bobbin piece with said secondary winding coil wound thereon into said covering element of said first bobbin piece.

10. The method of manufacturing the transformer according to claim 1 wherein said magnetic core assembly includes a first magnetic part and a second magnetic part.

Description:

FIELD OF THEINVENTION

The present invention relates to a transformer, and more particularly to a transformer for avoiding high-voltage spark or short circuit.

BACKGROUND OF THE INVENTION

A transformer has become an essential electronic component for voltage regulation into required voltages for various kinds of electric appliances. Referring to FIG. 1, a schematic exploded view of a conventional transformer is illustrated. Thetransformer 1 principally comprises a magnetic core assembly 11, a bobbin 12, a primary winding coil 13 and a secondary winding coil 14. The primary winding coil 13 and the secondary winding coil 14 are overlapped with each other and wound around awinding section 121 of the bobbin 12. A tape 15 is provided for isolation and insulation. The magnetic core assembly 11 includes a first magnetic part 111 and a second magnetic part 112. The middle portion 111a of the first magnetic part 111 and themiddle portion 112a of the second magnetic part 112 are embedded into the channel 122 of the bobbin 12. The primary winding coil 13 and the secondary winding coil 14 interact with the magnetic core assembly 11 to achieve the purpose of voltageregulation.

Since the leakage inductance of the transformer has an influence on the electric conversion efficiency of a power converter, it is very important to control leakage inductance. Related technologies were developed to increase coupling coefficientand reduce leakage inductance of the transformer so as to reduce power loss upon voltage regulation. In the transformer of FIG. 1, the primary winding coil 13 and the secondary winding coil 14 are overlapped with each other and wound around the bobbin12. As a consequence, there is less magnetic flux leakage generated from the primary winding coil 13 and the secondary winding coil 14. Under this circumstance, since the coupling coefficient is increased, the leakage inductance of the transformer isreduced and the power loss upon voltage regulation is reduced, the electric conversion efficiency of a power converter is enhanced.

In the power supply system of the new-generation electric products (e.g. LCD televisions), the transformers with leakage inductance prevail. For electrical safety, the primary winding coil and the secondary winding coil of this transformer areseparated by a partition element of the bobbin. Generally, the current generated from the power supply system will pass through an LC resonant circuit composed of an inductor L and a capacitor C, wherein the inductor L is inherent in the primary windingcoil of the transformer. At the same time, the current with a near half-sine waveform will pass through a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switch. When the current is zero, the power MOSFET switch is conducted. After ahalf-sine wave is past and the current returns zero, the switch is shut off. As known, this soft switch of the resonant circuit may reduce damage possibility of the switch, minimize noise and enhance performance.

As the size of the LCD panel is gradually increased, the length and the number of the lamps included in the LCD panel are increased and thus a higher driving voltage is required. Referring to FIG. 2, a schematic exploded view of a transformerused in the conventional LCD panels is illustrated. The transformer 2 of FIG. 2 principally comprises a magnetic core assembly 21, a first bobbin piece 22, a second bobbin piece 23, a primary winding coil 24 and a secondary winding coil 25. The firstbobbin piece 22 has a first side plate 26. The second bobbin piece 23 has a second side plate 27 and a plurality of partition plates 23a. Several winding sections 23b are defined by any two adjacent partition plates 23a. According to voltage dividingprinciple, the number of winding sections 23b may be varied depending on the voltage magnitude. In addition, a first base 26a and a second base 27a are extended from the first side plate 26 and the second side plate 27, respectively. Several pins 28and 29 are respectively arranged on the bottom surfaces of the first base 26a and the second base 27a.

For winding the primary winding coil 24 on the first bobbin piece 22, a first terminal of the primary winding coil 24 is firstly soldered on a pin 28a under the first base 26a. The primary winding coil 24 is then successively wound on the firstbobbin piece 22 in the direction distant from the first side plate 26. Afterward, a second terminal of the primary winding coil 24 is returned to be soldered onto another pin 28b under the first base 26a. For winding the secondary winding coil 25 onthe second bobbin piece 23, a first terminal of the secondary winding coil 25 is firstly soldered on a pin 29a under the second base 27a. The secondary winding coil 25 is then successively wound on the winding sections 23b of the second bobbin piece 23in the direction distant from the second side plate 27. Afterward, a second terminal of the secondary winding coil 25 is returned to be soldered onto another pin 29b under the second base 27a. Moreover, due to the partition plate 23a of the secondbobbin piece 23, the primary winding coil 24 is separated from the secondary winding coil 25, thereby maintaining an electrical safety distance and increasing leakage inductance of the transformer.

The winding structure of the transformer 2, however, still has some drawbacks. For example, since the second terminals of the primary winding coil 24 and the secondary winding coil 25 are returned to be soldered onto the pins 28b and 29b underthe first base 26a and the second base 27a, respectively, portions of these second terminals are disposed under the primary winding coil 24 wound on the first bobbin piece 22 and the secondary winding coil 25 wound on the second bobbin piece 23. Even ifthe second terminals are covered by insulating material, the creepage distance is insufficient. Under this circumstance, the transformer 2 is readily suffered from high-voltage spark or short circuit and eventually has a breakdown.

Therefore, there is a need of providing a transformer for avoiding high-voltage spark or short circuit so as to obviate the drawbacks encountered from the prior art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a transformer for avoiding high-voltage spark or short circuit so as to prevent damage of the transformer.

It is another object of the present invention to provide a transformer for reducing manufacturing cost.

In accordance with an aspect of the present invention, there is provided a transformer. The transformer includes a first bobbin piece, a second bobbin piece, a first pin, a second pin and a magnetic core assembly. The first bobbin piece has afirst channel therein. A primary winding coil is wound on the first bobbin piece. The second bobbin piece includes a first secondary side plate, a second secondary side plate opposed to the first secondary side plate, a plurality of partition platesbetween the first secondary side plate and the second secondary side plate, a wall portion between every two adjacent partition plates, and a secondary base extended from an edge of the first secondary side plate. A secondary winding section is definedby every two adjacent partition plates for winding a secondary winding coil thereon. A second channel is defined within the wall portion. The first pin is arranged on a bottom surface of the secondary base. The second pin includes a wire-arrangingpart, an insertion part and an intermediate part between the wire-arranging part and the insertion part. The wire-arranging part is protruded from the second secondary side plate. The intermediate part is buried in the wall portion. The insertion partis protruded from the bottom surface of the secondary base. A first terminal of the secondary winding coil is fixed on the first pin and a second terminal of the secondary winding coil is fixed on the wire-arranging part of the second pin. The magneticcore assembly is embedded within the first channel of the first bobbin piece and the second channel of the second bobbin piece.

In accordance with another aspect of the present invention, there is provided a method of manufacturing a transformer. First, a first bobbin piece is provided, wherein the first bobbin piece has a first channel therein and a primary windingsection. Second, a second bobbin is provided, wherein the second bobbin piece comprises a first secondary side plate, a second secondary side plate opposed to the first secondary side plate, a plurality of partition plates between the first secondaryside plate and the second secondary side plate, a wall portion between every two adjacent partition plates, and a secondary base extended from an edge of the first secondary side plate and having a first pin arranged on a bottom surface of the secondarybase, wherein a plurality of secondary winding sections are defined by every two adjacent partition plates, and a second channel is defined within the wall portion. Then a second pin is inserted into the second bobbin piece to penetrate through the wallportion and the second secondary side plate and form a wire-arranging part protruded from the second secondary side plate and an insertion part protruded from the bottom surface of the secondary base. Later, a primary winding coil is wound on theprimary winding section, a first terminal of a secondary winding coil is fixed on the first pin and then wound on the secondary winding sections, and a second terminal of the secondary winding coil is fixed on the wire-arranging part of the second pin. Finally, a magnetic core assembly is partially disposed within the first channel of the first bobbin piece and the second channel of the second bobbin piece.

The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic exploded view of a conventional transformer;

FIG. 2 is a schematic exploded view illustrating a transformer used in the conventional LCD panels;

FIG. 3 is a schematic exploded view of a transformer according to a first preferred embodiment of the present invention;

FIG. 4A is a schematic perspective view of the second bobbin piece shown in FIG. 3;

FIG. 4B is a schematic cross-sectional view of the second bobbin piece shown in FIG. 4A;

FIG. 4C is a schematic perspective view of the second bobbin piece shown in FIG. 4A having the winding coil wound thereon;

FIG. 5 is a schematic assembled view of the transformer of FIG. 3;

FIG. 6A is an exploded view illustrating a transformer set according to a second preferred embodiment of the present invention;

FIG. 6B is a schematic assembled view of the transformer set of FIG. 6A;

FIG. 7A is a schematic view of the second pin; and

FIG. 7B is a schematic cross-sectional view of the second bobbin piece having the second pin of FIG. 7A inserted therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose ofillustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.

Referring to FIG. 3, a schematic exploded view of a transformer according to a first preferred embodiment of the present invention is illustrated. The transformer 3 of FIG. 3 principally comprises a magnetic core assembly 31, a first bobbinpiece 32, a second bobbin piece 33, a primary winding coil 34 and a secondary winding coil 35. The magnetic core assembly 31 includes a first magnetic part 311 and a second magnetic part 312. The first leg 311a of the first magnetic part 311 and thefirst leg 312a of the second magnetic part 312 are arranged inside the first bobbin piece 32 and the second bobbin piece 33, respectively. The primary winding coil 34 and the secondary winding coil 35 interact with the magnetic core assembly 31 toachieve the purpose of voltage regulation.

The first bobbin piece 32 includes a primary base 321, a covering element 322 and a first channel 323. A primary winding section 324 is defined between the primary base 321 and the covering element 322 such that the primary winding coil 34 canbe wound on the primary winding section 324. It is preferred that the covering element 322, the primary winding section 324 and the primary base 321 are integrally formed. The covering element 322 is substantially a rectangular structure having areceptacle (not shown) therein. The first channel 323 penetrates through the primary base 321 and the primary winding section 324 and communicated with the receptacle of the covering element 322. The receptacle of the covering element 322 is providedfor receiving parts of the second bobbin piece 33 and the secondary winding coil 35 wound on the second bobbin piece 33, which will be described later. Accordingly, the primary winding coil 34 and the secondary winding coil 35 are separated from eachother by the covering element 322. Meanwhile, the first channel 323 of the first bobbin piece 32 and the second channel 335 of the second bobbin piece 33 are communicated with each other.

Alternatively, the first channel 323 of the first bobbin piece 32 and the second channel 335 of the second bobbin piece 33 are not communicated with each other but blocked by an insulating partition, which can be provided on the covering element322. For example, the covering element 322 is a hollow rectangular structure formed by five side plates and have an opening in the direction away from the primary winding section 324, so that parts of the second bobbin piece 33 are received in thereceptacle of the covering element 322 through the opening, wherein the side plate 322a of the covering element 322 which is close to the primary winding section 324 is served as an insulating partition to isolate the first leg 312a of the secondmagnetic part 312 from the primary winding coil 34 and to isolate the first leg 311a of the first magnetic part 311 from the secondary winding coil 35, especially to isolate the first leg 311a of the first magnetic part 311 from the secondary windingcoil 35 wound on the wire-arranging part 337a (as shown in FIG. 4C) of the second pin 337 so as to avoid high-voltage spark or short circuit due to insufficient safety distance. Moreover, by controlling the thickness of the side plate 322a, i.e. thethickness of the insulating partition that isolates the primary side and the secondary side, the leakage inductance of the transformer can be accordingly controlled. In addition, since the primary side and the secondary side are isolated via thecovering element and the insulating partition, the creepage distance is increased, and thus, the distance between the primary side and the secondary side can be reduced, so as to further reduce the integral length of the transformer.

In some embodiments, a plurality of L-shaped pin 325 are disposed on the primary base 321 of the first bobbin piece 32 for plugging onto a printed circuit board (not shown). The pins 325 are inserted into corresponding holes of the primary base32, and each pin 325 includes a first connection part 325a and a second connection part 325b, which are substantially vertical to each other and protruded from the edges of the primary base 321, wherein the pin 325 is plugged onto the printed circuitboard through the second connection part 325b. Preferably, the first connection part 325a and the second connection part 325b are formed integrally by bending a conductive pin made of conductive material, such as copper or aluminum, into the L-shapedpin 325, but not limited thereto. Besides, the L-shaped pin 325 can be easily assembled onto the primary base 321.

Hereinafter, an embodiment of winding the primary winding coil 34 will be illustrated as follows with reference to FIG. 3. First, a first terminal of the primary winding coil 34 is wound on and soldered on the first connection part 325a of onepin 325, then the primary winding coil 34 is wound through a trench 321a under the primary base 321 and wound around the primary winding section 324, and then wound through another trench 321a under the primary base 321, and finally wound on and solderedon the first connection part 325a of another pin 325. Since the terminals of the primary winding coil 34 are wound on the first connection parts 325a of the pins 325, and connected to the printed circuit board through the second connection parts 325b,the structural strength of the pins 325 can be enhanced and the integral height of the transformer can be reduced. Moreover, the evenness of the pins 325 would not be influenced due to that the terminals of the winding coil are not wound on the partwhich is connected to the printed circuit board (i.e. the second connection part 325b).

FIG. 4A is a schematic perspective view of the second bobbin piece 33 shown in FIG. 3. The second bobbin piece 33 includes a first secondary side plate 330, a second secondary side plate 338, a plurality of hollow partition plates 332, a wallportion 333 and a secondary base 331. The first secondary side plate 330, the second secondary side plate 338, the hollow partition plates 332, the wall portion 333 and the secondary base 331 have rectangular shapes. The first secondary side plate 330and the second secondary side plate 338 are arranged on opposite sides of the second bobbin piece 33 and have apertures therein. It is preferred but not limited that the first secondary side plate 330, the second secondary side plate 338, the pluralityof hollow partition plates 332, the wall portion 333 and the secondary base 331 are integrally formed.

The hollow partition plates 332 are parallel with the first secondary side plate 330 and the second secondary side plate 338. The wall portion 333 is arranged between the first secondary side plate 330 and the neighboring hollow partition plate332, between every two hollow partition plates 332, and between the second secondary side plate 338 and the neighboring hollow partition plate 332. The wall portion 333 is also in connection with the first secondary side plate 330, the second secondaryside plate 338 and the hollow partition plates 332 so as to form a second channel 335 therein. The first leg 312a of the second magnetic part 312 is embedded into the second channel 335. Moreover, a plurality of winding sections 334 are defined betweenthe first secondary side plate 330, the second secondary side plate 338, the hollow partition plates 332 and the wall portion 333 for winding the secondary winding coil 35 thereon.

The secondary base 331 is extended from an edge of the first secondary side plate 330 and also has an aperture therein corresponding to that of the first secondary side plate 330. A first pin 336 and a second pin 337 are arranged on thesecondary base 331 for plugging onto the printed circuit board (not shown). Furthermore, the first secondary side plate 330, the second secondary side plate 338, the hollow partition plates 332 and the secondary base 331 have corresponding notches 339.

FIG. 4B is a schematic cross-sectional view of the second bobbin piece 33 shown in FIG. 4A. As shown in FIGS. 4A and 4B, the second pin 337 includes a wire-arranging part 337a, an intermediate part 337b and an insertion part 337c. Theintermediate part 337b is buried in the wall portion 333 of the second bobbin piece 33 and arranged between the wire-arranging part 337a and the insertion part 337c. The intermediate part 337b is L-shaped. The wire-arranging part 337a is protruded fromthe second secondary side plate 338. The insertion part 337c is protruded from the bottom surface of the secondary base 331 to be inserted into a corresponding conductive hole of the printed circuit board, so that the transformer 3 is electricallyconnected to the printed circuit board. It is noted that, however, those ordinary skill in the art will readily observe that numerous modifications and alterations of the second pin 337 may be made while retaining the teachings of the invention. Forexample, the shape of the intermediate part 337b can be varied according to the profile of the second bobbin piece 33.

Hereinafter, an embodiment of winding the secondary winding coil 35 will be illustrated as follows with reference to FIG. 4C. First of all, a first terminal of the secondary winding coil 35 is wound on and soldered on the first pin 336. Thesecondary winding coil 35 is successively wound on the winding sections 334 from the first secondary side plate 330 to the second secondary side plate 338 through the notches 339. After a second terminal of the secondary winding coil 35 is wound on andsoldered onto the wire-arranging part 337a of the second pin 337, the secondary winding coil 35 is fixed on the second bobbin piece 33. As a consequence, the electricity generated from the secondary winding coil 35 is transmitted from the wire-arrangingpart 337a to the printed circuit board through the intermediate part 337b and the insertion part 337c. Since the second terminal of the secondary winding coil 35 is soldered onto the wire-arranging part 337a of the second pin 337 without the need ofreturning to the first pin side, the problem of causing high-voltage spark or short circuit is avoided.

FIG. 5 is a schematic assembled view of the transformer of FIG. 3. As shown in FIG. 5, the secondary base 331 of the second bobbin piece 33 includes a first sidewall 331a, a second sidewall 331b and a third sidewall 331c. A first engagingelement 331d (e.g. a raised block) is protruded from the first sidewall 331a. A second engaging element 331e (as shown in FIG. 4A) is disposed on the second sidewall 331b corresponding to the first engaging element 331d. The second engaging element331e (e.g. an indentation) has a complementary shape to the first engaging element 331d. Via the first engaging element 331d and the second engaging element 331e, the transformer 3 can be combined with another transformer (not shown) so that two or moretransformers can be arranged in a stack form. Optionally, the third sidewall 331c has a third engaging element 331f (e.g. a protrusion). In addition, a fourth engaging element 322b (e.g. a groove) is formed on the covering element 322 of the firstbobbin piece 32 corresponding to the third engaging element 331f. When the fourth engaging element 322b is engaged with the third engaging element 331f, the first bobbin piece 32 and the second bobbin piece 33 are combined together. Furthermore, afifth engaging element 321b (e.g. a raised block) and a sixth engaging element (not shown) corresponding to the fifth engaging element 321b are disposed on opposite sides of the primary base 321 of the first bobbin piece 32, which are similar to thefirst engaging element 331d and the second engaging element 331e of the secondary base 331 of the second bobbin piece 33, and are not redundantly described here.

For assembling the transformer 3, the second secondary side plate 338 of the second bobbin piece 33 and the secondary winding coil 35 wound on the second bobbin piece 33 are firstly embedded into the receptacle of the covering element 322 of thefirst bobbin piece 32. Accordingly, the primary winding coil 34 and the secondary winding coil 35 are separated from each other by the covering element 322. Next, the fourth engaging element 322b of the covering element 322 is engaged with the thirdengaging element 331f of the secondary base 331 of the second bobbin piece 33, so that the first bobbin piece 32 and the second bobbin piece 33 are combined together. Afterwards, the first leg 311a of the first magnetic part 311 and the first leg 312aof the second magnetic part 312 are embedded into the first channel 323 of the first bobbin piece 32 and the second channel 335 of the second bobbin piece 33, respectively. The assembled structure of the transformer 3 is shown in FIG. 5.

In the above embodiment, the resulting structure of the transformer 3 is substantially a rectangular solid. The appearance of the overall transformer may be varied according to the utility space and the performance requirement.

FIG. 6A is an exploded view illustrating a transformer set according to a second preferred embodiment of the present invention. In this embodiment, the transformer set is assembled by a first transformer 3 and a second transformer 4, which arearranged in parallel with each other. The first transformer 3 and the second transformer 4 are combined together via the engagement of the corresponding engaging elements on the primary base 321 and the secondary base 331 of the first transformer 3 andthe primary base 421 and the secondary base 431 of the second transformer 4. The first leg 311a and the second leg 311b of the first magnetic part 311 are embedded into the first channel 323 of the first transformer 3 and the first channel 423 of thesecond transformer 4, respectively. Likewise, the first leg 312a and the second leg 312b of the second magnetic part 312 are embedded into the second channel 335 of the first transformer 3 and the second channel 435 of the second transformer 4,respectively. The assembled structure of the first transformer 3 and the second transformer 4 is shown in FIG. 6B.

On the other hand, the present invention also provides a method for manufacturing a transformer. First, as shown in FIG. 3, a first bobbin piece 31 which includes a primary base 321, a first channel 323, a primary winding section 324 and acovering element 322 is provided, wherein the covering element 322 has a receptacle for receiving at least parts of a second bobbin piece 33. Second, a second bobbin piece 33 which includes a first secondary side plate 330, a second secondary side plate338, a plurality of hollow partition plates 332, a wall portion 333 and a secondary base 331 is provided, wherein a first pin 336 is arranged on the secondary base 331. The first secondary side plate 330 and the second secondary side plate 338 arearranged on opposite sides of the second bobbin piece 33, and the hollow partition plates 332 are disposed between the first secondary side plate 330 and the second secondary side plate 338. The wall portion 333 is arranged between the first secondaryside plate 330 and the neighboring hollow partition plate 332, between every two hollow partition plates 332, and between the second secondary side plate 338 and the neighboring hollow partition plate 332 so as to form a second channel 335 and aplurality of secondary winding sections 334. Meanwhile, during the molding process for forming the second bobbin piece 33, the second pin 337 is arranged in the mold in advance, so that the second pin 337 is disposed on the second bobbin piece 33 as thesecond bobbin piece 33 is formed, and includes a wire-arranging part 337a, an intermediate part 337b and an insertion part 337c, wherein the intermediate part 337b is buried in the wall portion 333 of the second bobbin piece 33 and arranged between thewire-arranging part 337a and the insertion part 337c, the wire-arranging part 337a is protruded from the second secondary side plate 338, and the insertion part 337c is protruded from the bottom surface of the secondary base 331 for plugging onto theprinted circuit board (as shown in FIG. 4B). Later, a primary winding coil 34 is wound on the primary winding section 324, and a first terminal of a secondary winding coil 35 is fixed on the first pin 336 and then wound on the secondary winding sections334, and subsequently, the second terminal of the secondary winding coil 35 is fixed on the wire-arranging part 337a of the second pin 337 on the second secondary side plate 338 (as shown in FIG. 4C). After the primary winding and the secondary windingare accomplished, parts of the second bobbin piece 33 are received in the receptacle of the covering element 322 of the first bobbin piece 32. Finally, a magnetic core assembly 31 is partially embedded within the first channel 323 of the first bobbinpiece 32 and the second channel 335 of the second bobbin piece 33, and the assembled structure of the transformer 3 is shown in FIG. 5.

In another embodiment, the second pin 337 can be inserted into the second bobbin piece 33 after the second bobbin piece 33 is formed. According to this embodiment, another method for manufacturing a transformer is provided. First, as shown inFIG. 3, a first bobbin piece 31 which includes a primary base 321, a first channel 323, a primary winding section 324 and a covering element 322 is provided, wherein the covering element 322 has a receptacle for receiving at least parts of a secondbobbin piece 33. Second, a second bobbin piece 33 which includes a first secondary side plate 330, a second secondary side plate 338, a plurality of hollow partition plates 332, a wall portion 333 and a secondary base 331 is provided, wherein a firstpin 336 is arranged on the secondary base 331. The first secondary side plate 330 and the second secondary side plate 338 are arranged on opposite sides of the second bobbin piece 33, and the hollow partition plates 332 are disposed between the firstsecondary side plate 330 and the second secondary side plate 338. The wall portion 333 is arranged between the first secondary side plate 330 and the neighboring hollow partition plate 332, between every two hollow partition plates 332, and between thesecond secondary side plate 338 and the neighboring hollow partition plate 332 so as to form a second channel 335 and a plurality of secondary winding sections 334. After the second bobbin piece 33 is formed, a second pin 337 is inserted into the secondbobbin piece 33 and penetrates through the wall portion 333 and the second secondary side plate 338, so as to form a wire-arranging part 337a, which is protruded from the second secondary side plate 338 in the front end, and then, the rear end of thesecond pin 337 is bended to form an insertion part 337c which is protruded from the bottom surface of the secondary base 331 for plugging onto a printed circuit board. Meanwhile, an intermediate part 337b is defined between the wire-arranging part 337aand the insertion part 337c and buried in the wall portion 333 of the second bobbin piece 33 (as shown in FIG. 4B). Later, a primary winding coil 34 is wound on the primary winding section 324, and a first terminal of a secondary winding coil 35 isfixed on the first pin 336 and then wound on the secondary winding sections 334, and subsequently, the second terminal of the secondary winding coil 35 is fixed on the wire-arranging part 337a of the second pin 337 on the second secondary side plate 338(as shown in FIG. 4C). After the primary winding and the secondary winding are accomplished, parts of the second bobbin piece 33 are received in the receptacle of the covering element 322 of the first bobbin piece 32. Finally, a magnetic core assembly31 is partially embedded within the first channel 323 of the first bobbin piece 32 and the second channel 335 of the second bobbin piece 33, and the assembled structure of the transformer 3 is shown in FIG. 5.

In this embodiment, since the second pin 337 does not need to be arranged in the mold in advance during the molding process of the second bobbin piece 33, the manufacturing cost in respect to the mold design and the quality control of the moldingarticle can be greatly reduced. In addition, to facilitate the insertion and positioning of the second pin 337, the second pin 337 can be designed to have a gradually increasing width, wherein the front end (i.e. the wire-arranging part 337a) has asmaller width, and the width of the second pin 337 is gradually increased at the intermediate part 337b, and further, the width of the insertion part 337c is restored to the normal pin width (as shown in FIG. 7A). Therefore, when the second pin 337 isinserted into the preserved hole on the second bobbin piece 33, the gradually increasing width facilitates the positioning and fixing of the second pin 337, and then the rear end of the second pin 337 is bended to form the insertion part 337c (as shownin FIG. 7B). It is noted that, however, those ordinary skill in the art will readily observe that numerous modifications and alterations of the second pin 337 may be made while retaining the teachings of the invention. For example, the second pin 337can also be designed to have an even width, and the insertion depth can be controlled by the insertion machine. Moreover, the second pin 337 can be bended to form the insertion part 337c in advance before the second pin 337 is inserted into the secondbobbin piece 33.

From the above description, since the second terminal of the secondary winding coil is soldered onto the wire-arranging part of the second pin without returning to the first pin side, the problem of causing high-voltage spark or short circuit isavoided. As a consequence, the possibility of causing breakdown of the transformer is minimized. Moreover, the second pin can be inserted into the second bobbin piece after the second bobbin piece is formed, so as to greatly reduce the manufacturingcost of the transformer.

While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, itis intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.